Coffee

Hey Team Diabetes blog readers! I hope that everyone’s second wave of midterms went well! A few updates to begin: last Wednesday was World Diabetes Day! It is the world’s largest diabetes awareness campaign, and it is celebrated on the birthday of Sir Frederick Banting, a Canadian scientist who co-discovered insulin with Charles Best in 1921. Not only that, but on November 18, our club hosted yet another one of our flagship Smash Volleyball Tournaments! Not only did we raise over $1800 dollars, there were 24 participating teams, which is as many as we have ever had! Look out on social media for when we promote our next fun fundraising event! The next one will be dodgeball!

Moving on, we will be summarizing and reviewing yet another article this month. This article is from 2004, but it was an interesting read because it is about something many of us are getting quite used to: coffee! The title of the article is Effects of Coffee Consumption on Fasting Blood Glucose and Insulin Concentrations (van Dam et. al., 2004). This study examined the effects of coffee (caffeine) on fasting blood glucose and insulin concentrations over a length of 2-4 weeks in healthy participants. These participants were regular coffee consumers (5+ cups / day) and did not have diabetes. In the first test, 40 volunteers were tested in two treatment groups in random order: the first group would use 70 g coffee grounds for four weeks, and the other group would abstain from coffee for four weeks. However, 14 participants did not complete this cross over study, so the results only had a sample size of 26 participants. In the second test, three treatments were given in random order for 2 week each: 870 mg of caffeine total (6 pills), regular paper-filtered coffee (52 g ground coffee/day), and placebo (6 cellulose pills).

The results showed that after 2-weeks, the coffee consumption group had higher fasting glucose concentrations, but it failed to show this after 4-weeks. However, the results in the table did not reach significance for the 2-week comparison either. Additionally, fasting insulin concentrations DID reach significance after the 4-week mark – it was higher in the coffee group than the control group. For the second test, no significant differences were observed between the 3 groups in regard to plasma glucose concentrations. However, for the plasma insulin concentrations, there was a 5% increase in the caffeine pill group, and 9% increase in the coffee group, compared to the control groups. Yet, these results also failed to reach significance.  If the difference with the placebo group is factored in, the percentage is even less significant. Accordingly, the only results that reached significance were the insulin concentration comparisons made at the 4-week mark in the first study. To the author’s credit, this was the only conclusion that they admitted to being significant as well. An increase in plasma insulin may be due to decreased insulin sensitivity from higher coffee (caffeine consumption) leading to higher insulin secretion. It is important to not mistake correlation with causation. A plethora of physiological mechanisms exist in the human body, which makes it difficult to pinpoint a biological observation to a particular pathway. That is why many studies just focus solely on delineating pathways themselves. Other studies have shown that increased coffee intake over a 5-day period leads to higher free fatty acid and epinephrine concentrations. Free fatty acids lower the ability of the liver to clear out insulin from the blood. Therefore, it cannot be concluded whether elevated insulin concentrations in the coffee consumption group is due to decreased liver clearance of insulin, higher insulin secretion, or maybe even both! Due to the short 4-week length and low sample size of this study, the support is weak for increased insulin sensitivity from coffee consumption. Additionally, the participants consume 5 cups of coffee per day, whereas most coffee drinkers will consume less than that. Therefore, in case if you are wondering if drinking too much coffee is putting you at risk for diabetes – that conclusion is not well-supported by this article. However, future studies can definitely build on the results of this one to make a stronger case for the effects of coffee consumption on insulin tolerance in the body.

Until then, remember that getting enough sleep every day is probably the best thing to do to stay awake for those morning classes. But if necessary, a coffee won’t hurt (provided your doctor allows you caffeine of course, of which there is decaf for). Catch the next blog before Christmas!

 

-Kevin Lu

VP Research, Team Diabetes uOttawa

 

Dam, R. M., Pasman, W. J., & Verhoef, P. (2004). Effects of Coffee Consumption on Fasting Blood Glucose and Insulin Concentrations: Randomized controlled trials in healthy volunteers. Diabetes Care,27(12), 2990-2992. doi:10.2337/diacare.27.12.2990

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